15. Buffers and titration

Question 1

How do biological buffers work?

Answer 1

They usually have functional groups which can be protonated or deprotonated to maintain the constant pH

Ex.: amino acids

Question 2

Explain amino acids as buffers

Answer 2

Question 3

Explain phosphorous acid buffers

Answer 3

Cellular fluids rely on the second dissociation (di-hydrogen phosphate)

Question 4

Explain the carbonic acid buffers

Answer 4

Question 5

What is the influence of exercise to the carbonic acid buffer system?

Answer 5

Exercise leads to increase in CO₂ in blood → should lower pH but it is kept stable by excess of HCO₃^- ions

Question 6

What is the curve for strong acid and strong base titration?

Answer 6

Question 7

What is the curve for weak acid and strong base titration?

Answer 7

Halfway point - buffer region (maintains a relatively stable pH until the buffer is exhausted → steep increase in pH)

Question 8

What are the main points in weak acid - strong base titration where pH can be calculated?

Answer 8

• Buffer region pH when certain amount of base is added
• Halfway point when half of acid is reacted
• Equivalence point when full neutralisation occurs (ex n(acid) = n(base))

Question 9

What is the titration graph for weak base and strong acid titration?

Answer 9

Question 10

How indicators work and what is the rule of thumb?

Answer 10

Question 11

How is the indicator chosen for a titration?

Answer 11

Pick according to the equivalence point pH (depends on strength of acid / base in titration)